I was sent one of these hubs by the manufacturer, Etekcity.
What do you get?
Using the hub
I connected the hub to the Pi and plugged into the hub an HDMIPi (with Pi inside), a keyboard, mouse and wifi dongle. Everything powered up nicely but the devices I plugged in to be recognised by the Pi failed to work. I believe this has something to do with it being a USB 3.0 hub, or else it has a chipset that is incompatible. So, that was a bit disappointing. However, having said that I did use a normal port for the HDMIPi/Pi rather than the 2.1A port and it worked perfectly. So, I would say that it would be very good for powering multiple Pis at once, but not as a strict ‘hub’ for devices for the Pi. With the 4A power supply, you’ll probably be fine powering up to 5 Pis (depending on what was plugged into their USB ports) at once.
I then used the hub with my laptop in the same way – with a keyboard, mouse and wifi dongle plugged in. I’m happy to report that it worked plugged into both a USB 2.0 port and also a USB 3.0 port. All the devices were recognised and worked flawlessly.
For use with the Pi, the hub is really only useful for powering multiple Pis, rather than as a ‘proper’ hub. However, it does work as a hub with a normal PC or laptop.